As a normal aspect of animal development and homeostasis, programmed cell death (apoptosis) plays an essential role in maintaining the physiological balance of appropriate cell numbers by opposing uncontrolled cell proliferation. Abnormal inactivation or activation of apoptosis can lead to uncontrolled cell growth or uncontrolled cell death and may result in human diseases such as cancer, neurodegenerative diseases, and autoimmune disorders. The broad, long-term objective of this application is to understand the molecular mechanisms underlying the activation of apoptosis and to use the knowledge from the study of apoptosis to facilitate development of new methods in treatment and prevention of cancers and other human diseases caused by inappropriate apoptosis. Apoptosis is controlled and executed by an evolutionarily conserved cell death pathway. At the heart of this pathway is a family of highly specific cell death proteases, the caspases, which are first synthesized as latent precursors or zymogens and later activated by specialized machinery named apoptosome. The activation of caspases initiates cell killing and antagonizes cell growth to maintain appropriate cell numbers. Importantly, both positive and negative regulators of apoptosome and caspase activation are found to act as tumor suppressor genes and oncogenes, respectively, indicating crucial roles of apoptosis regulators in oncogenic transformation. A combination of genetic and proteomic approaches have been carried out to identify new apoptosis regulators and signaling mechanisms. A genetic screen has identified three new genes that mediate the translocation of CED-4, a central component of the C. elegans apoptosome, from mitochondria to nuclear membrane during apoptosis, and may define new apoptosis signaling mechanisms. In parallel, a proteomic analysis has identified several promising CED-4-binding proteins that are potential regulators of the CED-4 apoptosome. The specific aims of this application are to: (1) identify, characterize and clone genes that mediate apoptotic CED-4 translocation; (2) characterize genetically and phenotypically CED-4-binding proteins from proteomic analysis; (3) perform biochemical and mechanistic analyses of cell death activation. These systematic genetic, biochemical, and cell biological analyses will lead to identification of new genes, signaling mechanisms, and pathways involved in apoptosis activation. Some of the molecules identified in these studies may turn out to be potential targets for therapeutic drug designs in curing cancers or other human diseases caused by inappropriate apoptosis.